(1) Field of the Invention
The present invention relates to the manufacture of books and, particularly, to improvements in the adhesive bonding of "hard" covers to inner books. More specifically, this invention is directed to apparatus for applying a uniform coating of adhesive to the shaped back of a book block prior to the mating of the book block with a cover and, especially, to devices for exercising control over the glue applicator roller of such adhesive applying apparatus. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
In the manufacture of books on a commercial scale, attachment of the cover to the back of the book block is accomplished by establishment of an adhesive bond. Thus, the gauzing, sticking-back and capitalling of a book requires the application of an adhesive to the shaped back, i.e., the spine side, of the book block. The adhesive is customarily transferred to the book block by means of a profiled applicator roller which is caused to contact the book block back.
In a typical adhesive application procedure, a profiled applicator roller contacts a "scoop" roller which, in turn, is partly immersed in a reservoir containing molten adhesive. Adhesive is transferred from the reservoir to the profiled applicator roller by the "scoop" roller and, in turn, a film of glue is deposited to the book back as the profiled applicator roller rolls along the back of the book block. In one example of the prior art, the profiled applicator roller is movable relative to the back of the book blocks in synchronism with the movement of book blocks as the blocks are transported by a conveying device with their backs directed upwardly.
Experience has proven that the creation of a film of adhesive which extends over the full surface of a shaped book block back cannot be ensured solely through the use of a profiled applicator roller. This inability to achieve gluing over the full surface of the book block arises from the fact that it is impossible for the profile of the applicator roller to exactly match the contour of the backs of all of the book blocks to be processed.
To amplify the above remarks, when the profile of the applicator roller is "flatter" than that of the book block back, a film of glue having approximately the shape of a parabola will be created on the book block and, most importantly, no adhesive will be deposited in the corner regions of the book block back. Conversely, if the applicator roller has a profile which is "steeper" than the shape of a book block back, a region in the center of the block back may receive no adhesive.
A procedure for overcoming the above-briefly discussed deficiencies associated with the use of prior art profiled adhesive applicator rollers is disclosed in European Patent 0 189 580. In accordance with this procedure, during the time the applicator roller is in contact with the book block back, the rotational speed thereof is increased. Restated, European Patent 0 189 580 suggests that the adhesive applicator roller be caused to rotate such that a region on its periphery which is in contact with the book block be moving at a speed which is greater than speed of advance of the book block by a factor of 10-20%. Additionally, in the interest of preventing contamination of the cut face of the book block at the trailing end thereof in the direction of book block movement, this European patent teaches the necessity of reducing the rotational speed of the applicator roller concurrently with its being lifted clear of the book block back.
Implementation of the improved technique described immediately above has required complex, and thus expensive, apparatus. The complexity of this apparatus has been increased by the provision of mechanisms which allow compensation for the height of the book blocks being processed. Such hardware complexity inherently has an adverse effect on reliability.